Method of making an acoustical tile and ceiling construction



p 1966 J. 5. PODGURSKI 3,245,063

METHOD OF MAKING AN ACOUSTICAL TILE AND CEILING CONSTRUCTION Filed Feb.10, 1961 2 Sheets-Sheet l INVENTOR. JOHN S. PODGURSKl BY @MW lie/ A ril12, 1966 J. s. PODGURSKI 3,245,053

METHOD OF MAKING AN ACOUSTICAL TILE AND CEILING CONSTRUCTION Filed Feb.10, 1961 2 Sheets-Sheet 2 INVENTOR. JOHN S. PoDcauRsm B OMWI4-$QQWW "HEL 5- United States Patent METHOD OF MAKING AN ACOUSTICAL TILE ANDCEILING CONSTRUCTION John S. Podgurski, Gypsum, Ohio, assignor to UnitedStates Gypsum Company, Chicago, Ill., a corporation of Illinois FiledFeb. 10, 1961, Ser. No. 88,340

4 Claims. (Cl. 264--112) This invention relates to a method of makingacoustical tile normally utilized in ceiling constructions. Moreparticularly, this invention relates to an improved method of makingacoustical tile with an impervious backing.

A popular type of acoustical tile is made following generally theprocedure set forth in US. Patent No. 1,769,519. According to theteachings of this patent, a mixture of granulated mineral wool, fillers,certain coloring materials, if needed, and a binder, particularly one ofan amylaceous nature, such as thick boiling starch, is used to form thebody of the tile. Various other materials may be added to give certainproperties to the tile. In preparing this acoustical tile, thecomposition, usually at a temperature of about 190 F., is placed uponsuitable trays which have been previously covered with paper, such asnewsprint, and then screeded to a suitable thickness with areciprocating edge. A pleasing surface, including elongated fissures,resembling that of travertine stone is normally obtained. Alternatively,by screeding in a different manner the surface can be made without thefissures. The trays are then placed in an oven, and dried or cured at atemperature of between 250 to 300 F., for from about 16 to about 18hours.

The dried sheets, called slabs, are removed from the mold, dressed onboth faces to provide smooth surfaces, to obtain the desired thickenessand to prevent Warping, and are then cut into tiles of a desired size.

Previous to this invention it had been assumed by those skilled in thisart that for maximum drying speed the moisture should leave from boththe bottom and the top surfaces of the drying slab and that covering thebottom surface with an impervious lamina would increase the drying time.Accordingly, the tray bottoms were made of foraminous material andcovered with thin, relatively unsized layers of paper so as tofacilitate the passage of Water out of the back surface of the tilethrough the paper. Drying the composition under these conditionsresulted in migration of the starch to both the bottom and top surfaceswhere it strengthened the surface areas. During the dressing operation,the face surface of the slab was normally sanded off to obtain apleasing smooth surface, thereby removing a portion of the face area ofhigh starch-concentration. The resulting tiles were found to warp unlessthe corresponding back surface area of high starch content was alsosanded off. Thus, the back surface of the slabs were dressed by sandingoff the paper and a portion of the hardened composition to compensatefor sanding of the other (face) side.

Removing the back surface of the slabs in the aforenoted process is notonly a time-consuming and costiy operation but also results in the lossof the paper and part of the cured composition, thereby necessitatingthe use and curing of extra material in initially forming the slabs.

Mineral fiber acoustical tiles, particularly the fissured type referredto above, are quite porous and thus readily transmit gases therethrough.Though high porosity is needed to give good sound absorption, a highdegree of porosity presents a disadvantage when the tiles are used incertain ceiling constructions, particularly suspended acousticalceilings with controlled ventilation systems, such for example asdescribed in US. Patents No. 2,692,- 547, 2,782,557, 2,807,993, and2,920,357. In such suspended ceilings the space immediately thereoverserves as a plenum chamber for receiving and distributing air underpressure. This air then passes through the ceiling, at a controlled ratethroughout the ceiling area, to the space below. When air passes throughfissures or other haphazard openings in the tile, the rate of flow isnot only unpredictable but also uncontrollable, thus making it diificultor impossible to obtain a uniform flow pattern, such as has been founddesirable in good air conditioning practice.

In addition, the porous nature of the mineral fiber acoustical tilesreferred to above permits transmission of hot gases of combustiontherethrough. This results in a markedly lowered fire rating forsurfaces formed of such tiles, and is especially undesirable insuspended ceiling systems where a special effort is often necessary toattain a maximum resistance to fire transmission.

It is therefore an object of this invention to set forth an improvementin the manufacture of mineral fiber acoustical tiles formed by drying aporous composition spread upon trays.

It is an object of this invention to provide a simple, economicalprocess of manufacturing improved mineral fiber acoustical tiles.

It is another object of this invention to provide a process ofmanufacturing mineral fiber acoustical tiles, obviating the step ofremoval of the back surface of the tile.

It is a further object of this invention to provide an improvement inthe drying of the aforesaid acoustical tile.

It is another object of this invention to provide an improved processfor making an acoustical tile, which has good acousticalcharacteristics, is impervious to the extraneous infiltration of gasestherethrough and which is simple and economical to manufacture.

Various other objects will readily occur to those skilled in the art towhich this invention pertains from the following description.

In carrying out this invention in one form, a new and improved mineralfiber acoustical tile is produced by placing a metal foil sheet in thebottom of a slab-forming pan, depositing, screeding, drying and curingan amylaceous binder-mineral fiber composition in the pan, removing theresulting slab, dressing only the face of the slab, and cutting the slabinto tiles. The resulting tiles include a foil layer covering and bondedto their entire back face. An improved plenum chamber ceilingconstruction may be formed by supporting a plurality of such tiles inedge to edge substantially co-planar relation to form a suspendedceiling comprising the lower wall of a plenum chamber. This constructionmay be formed with controlled openings therethrough to providecontrolled passage of gasses through the ceiling to the space below.

For a more complete understanding of the invention, reference should hehad to the drawings wherein:

FIG. 1 is a perspective view of a tile of the type forming the subjectof this invention;

FIG. 2 is a schematic diagram of equipment for carrying out a process ofmanufacture employing the teachings of this invention;

FIG. 3 is a perspective view of a suspended ceiling constructionutilizing tiles produced in accordance with the teachings of thisinvention; and

FIG. 4 is a perspective view of another suspended ceiling constructionutilizing tiles produced in accordance with the teachings of thisinvention.

FIG. 1 illustrates a novel acoustical tile 10 including a baked mineralfiber composition body 12 and a layer of foil 14, such as aluminum foil(exaggerated in thickness in the drawings), firmly bonded to the backsurface of the body. The tile is provided with slots or grooves forinstallation purposes, as will be later described.

The structure of tile 10' and certain of the advantages of providing atile of this construction are better illust-rated and understood withreference to the novel process of manufacture illustrated in FIG. 2.Trays 18 upon which the acoustical tile composition is to be spread andbaked are lined with a sheet of foil 20 instead of with paper, as in theprior process outlined above. An aluminum foil of about .00035, orsomewhat thicker, is preferred. The foil should be free from anycompound used during rolling which would adversely affect the bondbetween the foil and the mineral fiber composition. Foil sheet 2%] istaken from the roll 22 and spread evenly as a continuous sheet over theline of molds or trays 18. The portion of the foil sheet in each tray isthen covered and the tray filled with a plastic acoustical tilecomposition 24. Composition 24 is normally deposited in the trays, asthe trays, in abutting end to end relation, pass under feeder box 25 ona suitable conveyor, not shown. The feeder box is filled from the mixer28 by the conveyor 30'.

The composition 24 is an amylaceous binder-mineral fiber composition,but can vary appreciably in content. A typical batch is made as follows:

A starch binder is prepared from the following:

Thick boiling starch lbs 300 Calcium sulfate hemihydrate 'l bs 200 Watergals 595 The above is cooked at 180195 F. for 5 to 8 minutes and is thenready for use. Examples of presently available thick boiling starchesare Corn Products Companys starch products 3123 and 3173 and A. E.Staley Manufacturing Companys starch product Sta-Th-ik.

gallons of the above starch binder are placed in a mixer and 250 lbs. ofgranulated mineral wool are mixed therewith for a total mixing time, forthe entire formulation, of about 8 minutes to obtain an aqueous plasticmixture.

After the composition 24 has been placed upon the trays they pass underthe reciprocating screed bar 32, driven by the motor 34, which forms thefissures on the surface. A small rolly head 36 of the mix 24 collects inback of the bar. The sheet of foil is then severed between succeedingtrays, as by passing a knife (not shown) between the trays, and thefilled trays pass into the oven 38 where their contents are dried andcurred at a temperature between 250 and 300 F., for from 14 to 18 hours.

After the composition has dried and cured in the oven 33 to form slabs,the trays reach the position 46, where the slabs 42 are removed from thetrays. The foil is now firmly adhered to the body of the slab. The slabsare then dressed by passing them through a sander, not shown, to removeonly the top or face surface, and then through slitters, also not shown,to form tiles of the desired size. The resulting tiles have metal foilcovering and securely bonded to the entire back surfaces.

It is convenient to note at this point several new and unexpectedresults attributable to the novel process and novel acoustical tileconstruction described above.

It has been discovered that contrary to the aforenoted previouslyestablished opinion, replacement of the paper with aluminum foil doesnot increase the drying time of the slabs. In fact, there is someindication that the drying time is less beyond that reduction whichwould be due to the lesser thickness of the slab (referred to below).

In the practice of this invention, the foil prevents any significantremoval of moisture through the back surface and thus prevents anysignificant migration of starch toward this surface. The starch migratesonly to the top surface of the slab. The improved starch migrationpattern results in a greater concentration at the single sanding facewhere needed, or, if desired, permits a reduction in the amount ofstarch used. The resulting slab can be dressed by sanding the front faceonly, to obtain a desirable smooth surface and to trim the slab to thedesired tile thickness, without encountering warping in the resultingtile.

The temperature of ahe composition placed upon the tray is about 180 F.With the use of prior back sheets the temperature of the compositiondropped to about -F. before reaching the oven. It has been found thatwith the use of foil sheets, the temperature of the mix drops to onlyabout F. This favorable 30 increment represents a saving of heatrendering the process more eflicient and economical.

Thus, the use of metal foil as a back sheet provides a smooth even backsurface and eliminates the need for sanding off the back surface of theslab or tile. This permits the casting of thinner slabs, with aconsequent saving of material, and results in quicker drying and moreeconomical tile manufacture.

It can readily be seen from the above that a great number of unexpectedadvantages result from the novel use of the metal foil. The paper isreplaced, the sanding of the back is dispensed with, and the amount ofmaterial needed is decreased. There is a saving of heat, the foil doesnot adversely affect the drying, and an improved mineral fiberacoustical tile results. In addition, the foil aids in the removal ofthe cured composition or slabs from the trays and reinforces the backsurface of the tiles.

The suspended ceiling construction illustrated in FIG. 3 serves as onewall of a plenum chamber for controlled ventilation of the space belowand incorporates tiles produced in accordance with this invention toparticular advantage. In this type construction the air is uniformlydistributed, through openings properly spaced throughout the :ceilingarea, into the room below. The openings may be formed either in thetile, as shown in U.S. Patent No. 2,807,993, or in ported hollow runnersused to support adjacent rows of tile, as shown in U.S. Patent No2,920,357 and in 'FIG. 3.

As illustrated in FIG. 3, the foil backed tiles 10 are supported on theported runners 44 and similar cross members 50, with the foil backupwardly disposed. The runners are supported by Wires 46 attached to thestructure, not shown, of the upper boundary of the room in which theceiling is supported. The entire lenum chamber is not shown but normallyconstitutes the enclosure defined by the suspended ceiling, the upperbound ary of the room, and the lateral walls of the room extendingbetween the upper boundary and the suspended ceiling. Air is introducedinto the plenum chamber and passes in a well distributed and uniformrate through ports 48 in the runners 44 and ports 51 in cross members50. The opening in these ports may be adjustable to afford control ofthe airflow. The runners along with the cross members are modularlyspaced such as 2 ft. on centers. The cross members are attached to theprimary runner by means of clips, not shown. The tiles rest upon theledges forming the lower portion of the runners and cross members, withthe tile edges forming the joints between adjacent tiles not sosupported being reinforced by spline members 52 placed into the grooves16 of each tile. The spline members are formed from sheet metal with aslight reinforcing ridge extending down the center. It is important inthis type of construction that there is a close fit between the splinemembers and the grooves so as to prevent any passage of air through thejoint.

' The ceiling construction of FIG. 3 maintains the pleasmg appearanceand functional advantage arising from the fissured and/or porouscharacter of the tile. At the same time, this ceiling is impervious tothe passage of fluids except through the controlled ports 48 and 51. Thenet results are more accurate distribution and control of the airflowing from the plenum chamber into the room below and the allowance ofhigher pressures in the plenum chamber.

The ceiling 53 illustrated in FIG. 4 employes tile produced according tothe teachings of this invention and is well suited for asound correctingsuspended ceiling construction having high resistance to fire. In thisconstruction the tiles are joined together and supported by sheet metalflanges or splines at all the joints, whereby the passage of gasesthrough the joints between adjacent tile is substantially eliminated.The foil backed mineral fiber tiles are supported on flanged runners 54by the lower flanges 56 engaging the grooves or rabbets extending alongthe edges of adjacent tiles. The edges of adjacent tiles not directlysupported on the runners .are joined by splines 52. Flanged runners 54are attached to the channels 58 by means of clips 60. The channels aresupported by Wires 62 which are attached to the structure above, notshown. Ceiling 53 extends between the walls of the room in which it issuspended and no open ports are provided in this construction. Theresult is a substantially impervious mineral fiber tile ceiling whichprevents the passage of hot gases either through or around the tile.When properly erected, this type of construction has provided high firerating test results. The foil stops the passage of the hot gas throughthe body of the tile while the use of the spline members and the flangerunners prevents any passage through the joints, between adjacent tile.Thus, there is \a barrier to the passage of hot gases, which contributesto high fire ratings.

It has been found that the use of a foil across the entire back surfaceof mineral fiber acoustical tile, such as set forth above, will notadversely affect the sound absorption characteristics thereof. In fact,there is an unexpected increase in the sound attenuation factor. Forinstance, in structures embodying this invention, attenuation factors ashigh as 45 decibels have been attained as compared with about 31.5decibels without the aluminum foil.

It will thus be seen that a new and improved method of making acousticaltile has been provided. A molded mineral fiber acoustical tile andmethod of providing the same are disclosed in which a layer of aluminumfoil extends over and is conterminous with the back surface of the tileand is made a part thereof during its manufacture by spreading thecomposition forming the body of the tile upon a sheet of foil applied asa liner over the bottom of a mold. The step of sanding the back surfaceis eliminated with consequent saving in labor and material. There aresignificant improvements in drying of the tile. The resultant tile maypresent a porous and/ or fissured lower surface to obtain goodacoustical characteristics and pleasing appearance but are stillimpervious to passage of gases therethrou-gh and are economical toproduce. Such tile may be utilized to provide a ceiling constructionwhich facilitates control and uniform distribution of air through asuspended ceiling of mineral fiber acoustical tile from a plenum formedby the ceiling and the structure thereabove. The tile provides apleasing appearance and equal or improved acoustical properties whilepreventing any passage of air therethrough so that properly spacedopenings to give the desired air distribution can be used withouterratic and/ or extraneous flow of air through random fissures, highporosity areas, and the like, of varying degrees of air transmission.Further, in structures without intentionally formed openings, tilesproduced in accordance with this invention facilitate obtaining a highfire rating.

While particular embodiments of the invention have been shown, it willbe understood, of course, that the invention is not limited theretosince modifications may be made by those skilled in the art in light ofthe foregoing teachings. It is, therefore, contemplated by the appendedclaims to cover any such modifications as fall within the true spiritand scope of the invention.

I claim: p I p 1. A process for manufacturing non-warping acousticaltile comprising the steps of preparing an aqueous plastic compositionincluding mineral fiber material and an amylaceous binder for formingthe body of such tile, providing a mold tray, covering the bottom ofsaid tray with sheet material impervious to passage of water vaportherethrough, depositing and spreading said aqueous plastic compositionin said mold tray over said sheet material to form a body-forming layerof said composition, exposing said composition on said sheet material toa heating and drying environment whereby said composition is driedWithin substantially the same time as that required to dry the samecomposition on a pervious sheet under the same drying conditions, andthereby forming a slab comprising a layer of dried porous compositionhaving said impervious sheet material extending over and bonded to theback side thereof, dressing only the face side of said slab, and cuttingsaid slab to form acoustical tile having said sheet material extendingover and bonded to the back side thereof.

2. A process for manufacturing non-warping acoustical tile comprisingthe steps of preparing an aqueous plastic composition including mineralfiber material and an amylaceous binder for forming the body of suchtile, providing a mold tray, covering the bottom of said tray with sheetmaterial comprising a sheet of aluminum foil, depositing and spreadingsaid aqueous plastic composition in said mold tray over said foil toform a body-forming layer of said composition, exposing said compositionon said foil to a heating and drying environment whereby saidcomposition is dried within substantially the same time as that requiredto dry the same composition on a pervious sheet under the same dryingconditions, and thereby forming a slab comprising a layer of driedporous composition having said foil extending over and bonded to theback side thereof, dressing only the face side of said slab, and cuttingsaid slab to form acoustical tile having said foil extending over andbonded to the back side thereof.

3. A process for manufacturing non-warping acoustical tilecomprising thesteps of preparing a heated aqueous plastic composition includingmineral fiber material and starch for forming the body of such tile,providing a mold tray, covering the bottom of said mold tray with asheet of aluminum foil, depositing and screeding said heated aqueousplastic composition on said foil in said mold tray to form abody-forming layer of said composition having a fissured surface,placing said heated composition, on said foil, in an oven while stillhot, further heating and drying said composition on said foil in saidoven at an elevated temperature to form a slab comprising a layer ofdried porous composition having said aluminum foil extending over andbonded to the back side thereof, dressing only the face side of saidslab, and cutting said slab to form acoustical tile having said aluminumfoil extendin g over and bonded to the back side thereof.

4. A process for manufacturing non-warping acoustical tile comprisingthe steps of preparing an aqueous plastic composition including mineralfiber material and an amylaceous binder for forming the body of suchtile, providing a mold tray, covering the bottom of said tray with sheetmaterial comprising a sheet of metal foil, depositing and spreading saidaqueous plastic composition in said mold tray over said foil to form abody-forming layer of said composition, exposing said composition onsaid foil to a heating and drying environment at a temperature aboveabout 250 F., to dry said composition, and thereby forming a slabcomprising a layer of dried porous com position having said foilextending over and bonded to the back side thereof, dressing only theface side of said slab, and cutting said slab to form acoustical tilehaving said sheet material extending over and bonded to the back sidethereof.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS King et a1 161-41 Kliefoth.

Miller 154-445 Stranahan 20-4 Parkinson 20-4 Brown 264-122 Anderson18-475 Kro-pay 181-331 Willey 18-475 Tarriare 264-256 Page 20-4 Knight264-256 Ericson 20-4 Holtsford 181-331 Ericson 20-4 Sabine 20-4 Hanson181-331 Jordan 20-4 ALEXANDER H. BRQDMERKEL, Primary Examiner.

JACOB NACKENOFF, WVILLIAM I. MUSHAKE,

Examiners.

1. A PROCESS FOR MANUFACTURING NON-WARPING ACOUSTICAL TILE COMPRISINGTHE STEPS OF PREPARING AN AQUEOUS PLASTIC COMPOSITION INCLUDING MINERALFIBER MATERIAL AND AN AMYLACEOUS BINDER FOR FORMING THE BODY OF SUCHTILE, PROVIDING A MOLD TRAY, COVERING THE BOTTOM OF SAID TRAY WITH SHEETMATERIAL IMPERVIOUS TO PASSAGE OF WATER VAPOR THERETHROUGH, DEPOSITINGAND SPREADING SAID AQUEOUS PLASTIC COMPOSITION IN SAID MOLD TRAY OVERSAID SHEET MATERIAL TO FORM A BODY-FORMING LAYER OF SAID COMPOSITION,EXPOSING SAID COMPOSITION ON SAID SHEET MATERIAL TO A HEATING AND DRYINGENVIRONMENT WHEREBY SAID COMPOSITION IS DRIED WITHIN SUBSTANTIALLY THESAME TIME AS THAT REQUIRED TO DRY THE SAME COMPOSITION ON A PREVIOUSSHEET UNDER THE SAME DRYING CONDITIONS, AND THEREBY FORMING A SLABCOMPRISING A LAYER OF DRIED POROUS COMPOSITION HAVING SAID IMPERVIOUSSHEET MATERIAL EXTENDING OVER THE BONDED TO THE BACK SIDE THEREOF,DRESSING ONLY THE FACE SIDE OF SAID SLAB, AND CUTTING SAID SLAB TO FORMACOUSTICAL TILE HAVING SAID SHEET MATERIAL EXTENDING OVER AND BONDED TOTHE BACK SIDE THEREOF.